1. Field of the Invention
Exemplary aspects of the present invention generally relate to a process cartridge detachably installable in an image forming apparatus, and more particularly to a process cartridge constructed of a first sub-unit that holds an image carrier and a second sub-unit that holds a developer bearing member, and an image forming apparatus including the process cartridge.
2. Description of the Related Art
Related-art image forming apparatuses, such as copiers, printers, facsimile machines, and multifunction devices having two or more of copying, printing, and facsimile capabilities, typically form a toner image on a recording medium (e.g., a sheet of paper, etc.) according to image data using, for example, an electrophotographic method. In the electrophotographic method, for example, a charger charges a surface of an image carrier (e.g., a photoconductor); an irradiating device emits a light beam onto the charged surface of the photoconductor to form an electrostatic latent image on the photoconductor according to the image data; a developing device develops the electrostatic latent image with a developer (e.g., toner) to form a toner image on the photoconductor; a transfer device transfers the toner image formed on the photoconductor onto a sheet of recording media; and a fixing device applies heat and pressure to the sheet bearing the toner image to fix the toner image onto the sheet. The sheet bearing the fixed toner image is then discharged from the image forming apparatus.
The photoconductor and the developing device that holds a developer bearing member such as a developing roller are often formed together as a single integrated process cartridge detachably installable in the image forming apparatus.
In the process cartridge, a precise gap between the image carrier and the developer bearing member must be provided, without damage to the image carrier and the developer bearing member upon assembly of the process cartridge, in order to achieve high-quality images; i.e., images having a uniform image density.
There is known a process cartridge constructed of a first sub-unit that holds the image carrier and a second sub-unit that holds the developer bearing member. First and second positioning members that position the image carrier and the developer bearing member are provided at both ends of each of the image carrier and the developer bearing member in a longitudinal direction. Specifically, the first positioning member is fixed to one end of each of the first and second sub-units in the longitudinal direction with screws, and the second positioning member is fixed to the opposite end of one of the first and second sub-units in the longitudinal direction with screws.
As a result, a precise gap between the image carrier and the developer bearing member is accurately and evenly provided across the longitudinal direction without a failure of positioning of the image carrier and the developer bearing member in the longitudinal direction.
However, upon attachment of the first and second positioning members to the first and second sub-units, the image carrier, which is exposed outside the first sub-unit, and the developer bearing member, which is exposed outside the second sub-unit, may contact each other, possibly damaging the surface of the image carrier or the developer bearing member.